FACT SHEET 2: Polar bears depend on sea ice Projections of sea ice decline in the future spell trouble. Forecasts of summer sea ice from a range of climate models suggest reductions of 50 % or more by 2050, with some models projecting the complete disappearance of summer sea ice in a similar time frame. Such reductions in sea ice will drastically shrink marine habitat for polar bears, walrus, ice-inhabiting seals, and some seabirds, pushing some species toward extinction. Ice-living seals It is difficult to imagine the survival of ringed seals and Ice-living seals, including the ringed seal, ribbon seal, polar bears in the absence of summer sea ice. and bearded seal, are particularly vulnerable to projected reductions in Arctic sea ice because they give The polar bear birth to and nurse their pups on the ice and use it as a Polar bears are intimately tied to the sea ice, where they resting platform. They also do much of their foraging hunt ringed seals and other ice-associated seals, and use on the ice. Ringed seals are likely to be the most highly ice corridors to move from one area to another. affected species of seal because all aspects of their lives Pregnant females build their winter dens in areas with are tied to sea ice. They require sufficient snow cover thick snow cover on land or on sea ice. When females to construct lairs and the sea ice must be stable enough emerge from their dens with their cubs, the mothers in the spring to successfully rear young. Earlier ice have not eaten for 5 to 7 months. Their seal hunting break-up could result in premature separation of success, which depends on good spring ice conditions, mothers and pups, leading to higher death rates among is essential for the family's survival. Changes in ice newborns. extent and stability are thus of critical importance. The earliest impacts of warming would be expected to occur at the southern limits of the polar bears' distribution, such as James and Hudson Bays; such impacts have already been documented in recent years. Later formation and earlier break-up of sea ice means a longer period of fasting annually for female polar bears, and their reproductive success is tightly linked to their fat stores. Females in poor condition have smaller litters and smaller cubs that are less likely to survive. Climate change could also increase bear deaths directly. For example, increased frequency or intensity of spring rains could cause dens to collapse, resulting in the death of females and cubs. Earlier spring break up of ice could separate traditional den sites from spring feeding areas, and young cubs forced to swim long distances from breeding areas to feeding areas would not be likely to survive. The only foreseeable option that polar bears would have is to adapt to a land-based summer life-style, but competition, risk of hybridization with brown and grizzly bears, and increased human interactions would then present additional threats to their survival as a These two images, constructed from satellite data, compare arctic species. The loss of a pinnacle species such as the polar sea ice concentrations in September of 1979 and 2003. bear is likely to have significant and rapid consequences September is the month in which sea ice is at its yearly minimum and for the ecosystems they currently occupy. 1979 marks the first year that data of this kind became available in meaningful form. The lowest concentration of sea ice on record was in September of 2002 and 2003 was very close to that record low. Cascading impacts on species These changes will have significant implications for the Climate-related changes are likely to cause cascading ability of caribou and reindeer populations to find food impacts involving many species of plants and animals. and raise calves. Future climate change could thus Compared to ecosystems in warmer regions, Arctic mean a potential decline in caribou and reindeer systems generally have fewer species filling similar roles. populations, threatening human nutrition for Thus when Arctic species are displaced, there can be indigenous households and a whole way of life for important implications for species that depend upon Arctic communities. them. For example, mosses and lichens are particularly vulnerable to warming. Because these plants are Aquatic mammals and waterfowl important winter food sources for reindeer/caribou The distribution of aquatic mammals and waterfowl and other species and are the base of important food will likely extend northward as habitats change with chains, their decline will have far-reaching impacts warming. Seasonal migration is also likely to occur throughout the ecosystem. If reindeer and caribou earlier in spring and later in fall if temperatures are populations decline, that will impact species that hunt warm enough. Breeding ground suitability and access to them, including wolves, wolverines, and human beings, food will be the primary drivers of changes in as well as species that scavenge on them, such as Arctic migration patterns. For example, wetlands are foxes and various birds. Because some local important breeding and feeding grounds, and as communities are particularly dependent on permafrost thaws, more wetlands are likely to appear, reindeer/caribou, their well-being will also be impacted. promoting the earlier northward migration of southerly wetland species or increasing the abundance and Ice crust diversity of current high latitude species. However, a Ice crust formation resulting from freeze-thaw events parallel earlier timing of the availability of local food affects most Arctic land animals by encapsulating their must also occur for these outcomes to be realized. food plants in ice, severely limiting forage availability and sometimes killing the plants. Lemmings, musk Mammal and bird species moving northward are likely oxen, and reindeer/caribou are all affected, and to carry new diseases and parasites that pose new dramatic population crashes resulting from ice crusting threats to arctic species. Another potential downside of due to freeze-thaw events have been reported and their the northward migration of southerly species is that frequency appears to have increased in recent decades. they may out-compete northern species for habitat and The projected winter temperature increase of 6°C by resources. Northerly species may have diminished late this century (average of the five ACIA model reproductive success as suitable habitat either shifts scenarios) could result in an increase of alternating northward or perhaps declines in availability or access. periods of melting and freezing. Inuit of Nunavut in Canada report that caribou numbers decrease in years when there are many freeze- thaw cycles. Swedish Saami note that over the last decade, autumn snow lies on unfrozen ground rather than on frozen ground in summer grazing areas and this results in rotten and poor quality spring vegetation. Caribou and reindeer Caribou and reindeer are of primary importance to inland peoples throughout the Arctic for food, shelter, fuel, tools, and other cultural items. Caribou and reindeer herds depend on the availability of abundant tundra vegetation and good foraging conditions, especially during the calving season. Climate-induced changes to Arctic tundra are projected to cause vegetation zones to shift significantly northward, reducing the area of tundra and the traditional forage for these herds. Freeze-thaw cycles and freezing rain are also projected to increase.